E10 New Fuel Megathread [Consolidated for all E10 discussion]

Hi was wondering when the new fuel E10 comes in next year will it effect the cars that have been mapped… Was looking into having my car mapped but is it better to wait till after the fuel is introduced …a answer from the tuning guys would be good

Mine is remapped and used it for 2 weeks last year in Europe with no problems :+1:

This is a very interesting question, so hopefully some experienced tuners can chip in.
My take is:

  • MX5 NA and NB are said to be incompatible with e10. There must be an official line on this. Post 2005 cars are OK
  • E5 and E10 95RON are the same octane rating so should respond to the same tuning, so no issues there.
  • E10 contains ‘less energy’ than E5, so will use more fuel to deliver the same performance. Tuning does not need to be adjusted to compensate, you just run more throttle. Unlikely to be noticeable in practice.
  • Higher octane ratings are available with higher E content, but unless you are racing, I see little point in tuning to take advantage of that.

In France most pumps are E10, but there are still some E5 pumps. Even in supermarkets you can find E5 fuel dispite the price competition. I would be very surprised if the UK eliminates availability of E5 when so many older cars are incompatible with E10.

In America I usually fill hire cars with the cheapest fuel, which has a much higher E content. But this then runs about 25% to 30% less MPG, so cancels out the saving made.

So my take is, if you want to go down the tuning route, for day to day driving (not max performance SantaPod time) just get it done and enjoy the benefits now. Much more will come into the public arena before E5 is phased out, so you should be able to carry on using the same fuel for some time.

Be very interested to hear the tuners’ take on this.

They’re not said to be compatible. That’s not the same thing as said not to be compatible.

Mazda made them before e10 compatibility was something they required of all their parts suppliers so they’re not in a position to guarantee that everything they put into a car they built 30 years ago is e10 compatible.

From what I can gather is 2000 on should be ok…its all to do with what e10 does i;e rusts parts out like petrol tank sure someone will come up with a list of negatives that will happen

I read somewhere that the issue with E10 and Mk1 / Mk2 is the rubber pipework will breakdown.

Many rubbers and plastics are not suitable for continual exposure to alcohol. Over time they soften/disolve/breakdown. Two week trip through France maybe fine, running for a year on the stuff, not fine. Think about fuel lines, fuel system gaskets, plastic components in petrol tanks, fuel filters, etc.
Some alloys are also affected, caused issues on some carburettors.

It is also water absorbing, which can lead to the internal rusting of fuel tanks etc. It doesn’t inherently cause rust, it is the storage over time that results in the rust - daily driver will be fine, classic parked up over winter may have issues.

All cars sold since 2011 (I think) must by law be fine to run on e10, many produced before that are fine, just depends what the manufacturer used for all those various components.


Super unleaded like the type sold by Shell will still be available for a long time and you should be using that anyway.


Yep, my Eunos is measurably better on 99 vintage!


Mazda have said that models introduced during and after 2002 are cleared for use with e10 fuel, so that’s NC onwards.

Good answer and thanks.:+1:

Just a query though.
Would that not include the MK 2.5 cars (produced from 2002) onwards as its from 2002?

The wording says “models introduced” and they give the example of Mazda6 GG/GY, to me that means 5th generation cars.

1 Like

I assume from this, Page 11.
"E10 petrol is cleared for use in all models with petrol engines introduced in and from the year 2002, Mazda6 (GG/GY) and models with petrol engines introduced thereafter, i.e:
Mazda2: DY/DE.
Mazda3: BK/BL.
Mazda5: CR/CW.
MX-5: NC.
Mazda6: GG/GY/GH.
CX-5: KE.
CX-7: ER.
CX-9: TB.
RX-8: SE.

A- I read it as (because of the comma after 2002) as all petrol engines made and introduced from 2002.

B- Also the Mazda6 GG/GY. (The Mazda 6 is quoted and not as an “i.e for example?”

C- Then the list of cars introduced thereafter, (i.e new models which includes the NC)

Just my opinion, but not the best worded document for Mazda cars.

This is an interesting issue and one I’m curious to know more about. Water in the bottom of steel petrol tanks can make them rust of course but, so far as I know, additives designed to get rid of water in petrol (by making it mix with the fuel) are basically ethanol. So having ethanol in the petrol anyway will tend to dry the fuel tank. Of course in the era of vented petrol tanks, having ethanol in the fuel of a car in storage would gradually absorb as much moisture as it could from the air. Maybe as temperatures changed that could lead to water coming out of solution in the tank, I don’t know. But is that still an issue in the era of sealed fuel tanks? Surely the systems carefully designed to keep petrol fumes in will also keep moisture out.

Does anyone know more about this issue, in 1990s cars rather than say 1960s ones?

One thing for certain, it seems I’ll have to put super unleaded in my lawnmower from next year!

1 Like

Should make mowing the lawns quicker then.


Makes it ever so much easier to start!

Mine is a thirty-five year old Qualcast Suffolk Punch with Briggs & Stratton engine. When I switched the Vextra to V-Power (silk purse from sows ear improvement) the mower also got the same diet and instead of five or ten pulls to start from cold (even when new) it now always starts second pull, or sometimes third if the choke was not quite full on first time.

Side note, does anyone have a spare back roller? First breakdown, split roller now held together by gaffer tape because no stock anywhere and no longer made.

Any good?

(My throwaway comment has taken this massively off topic - sorry!)

1 Like

How did we get from will e10 effect a mapped car to a lawn mower…

Ordered. Many thanks.
Sorry for veering off-topic but it has saved me from buying a new mower!
Off-topic branch now closed!